Page 63 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 2-36 Benign Growths

Seborrheic
keratosis (close up)
SEBORRHEIC KERATOSIS

One of the most commonly encountered of all benign
skin growths is the seborrheic keratosis. These growths
come in all sizes and shapes and invariably can be found
on any human older than 40 years of age. They com-
monly begin in the fourth decade of life and tend to
increase in number over one’s lifetime. They have no
malignant potential but are often brought to the atten-
tion of physicians because they can mimic other skin
growths, most importantly malignant melanoma.
Clinical Findings: Seborrheic keratoses are found
equally in males and females, and they are seen in all
races. They begin to manifest in the third to fifth
decade of life and continue to increase in number there-
after. They come in various sizes and shapes. Some are
quite small, whereas others can be 5 to 6 cm in diam-
eter. They occur almost exclusively in sun-exposed
regions of the body. The classic description is that of a
1- to 2-cm plaque with a “stuck-on” appearance and
small horn cysts. Most commonly flesh colored, they
can also be tan, brown, or almost black. It is for this
reason that they are occasionally mistaken for mela-
noma. Most individuals have a few scattered keratoses,
but not infrequently a patient has thousands of these
skin growths. Seborrheic keratosis low power. Acanthotic epidermis
Many clinical variants of seborrheic keratosis can be
seen. Stucco keratoses are small (1-5 mm), gray-tan with overlying orthokeratosis. Multiple seborrheic keratosis lesions
papules with a stuck-on appearance or thin patches
on the lower extremities. Dermatosis papulosis is a
condition in which multiple seborrheic keratoses occur
on the face and neck. This condition has a definite
inheritance pattern.
Some seborrheic keratoses are smooth surfaced, but Dermatosis
more commonly they have a pebbly or dry, rough papulosis nigrans
surface. They have a characteristic stuck-on appear-
ance, and in some instances they are easily removed by
gently peeling from one side. These growths can easily
become irritated or inflamed. The resulting pain,
itching, or bleeding often brings the patient to medical
treatment.
The sign of Leser-Trélat is the rapid onset of
multiple seborrheic keratoses associated with an under-
lying internal malignancy. This sign has not been vali- Stucco keratosis
dated and is not a reliable indicator of an internal
malignancy.
Histology: There is a well-circumscribed prolifera-
tion of keratinocytes. They have an exophytic growth
pattern. The keratinocytes show acanthosis and hyper-
keratosis. Marked papillomatosis is also commonly
encountered. Two types of cysts are seen within the
seborrheic keratosis. The horn cyst develops within the
epidermis and is made of a keratin-filled cystic space
with a surrounding granular cell layer. A pseudo-horn
cyst is formed by an invagination of the stratum
corneum into the underlying epidermis. Multiple his-
tological subtypes have been described.
Pathogenesis: The formation of this benign epider-
mal tumor is not fully understood. It is caused by a
proliferation of keratinocytes within the epidermis. The human papillomavirus has been proposed but has yet to Another extremely effective method of removal that can
location in sun-exposed skin and the increasing number be proven. be done in the office is cryotherapy followed by a light
of lesions with increasing age has led some to believe Treatment: These keratoses require no therapy. If curettage; this also allows for histological evaluation.
that they are caused by a local suppression of the they become inflamed or irritated, a simple shave biopsy Occasionally, dark brown or black seborrheic keratoses
immune system that results in the epidermal prolifera- removal is curative. Cryotherapy and curettage are often can mimic melanoma, and in other cases a melanoma
tions. A definitive inheritance pattern has not been used to treat these benign skin growths, and both are may arise adjacent to a seborrheic keratosis and mislead
discovered, but these keratoses show some genetic pre- extremely effective. After cryotherapy treatment, a the clinician. If there is ever a doubt that the growth
disposition. Chromosomal analysis of these tumors has blister usually forms at the base of the seborrheic kera- could be a melanoma, a biopsy is required. This allows
not revealed any chromosomal defects. A link with the tosis, and within a day or two the keratosis falls off. for pathological confirmation of the diagnosis.

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 49